1. Field of the Invention
The present invention relates to an improved hypodermic syringe and more particularly to a syringe with a means for insuring that the user or others will not accidentally be injured, thereby risking infection, once a needle has been used.
2. Description Relative to the Prior Art
In recent years, particularly since the onset of the AIDS epidemic and Hepatitis "B", many attempts have been made to provide hypodermic syringes with means for preventing accidental injury with a used needle, and for preventing a second use of a used needle. Various prior art references, for example U.S. Pat. Nos. 4,655,751, 5,197,953, 5,154,698, 5,057,079, 5,053,018, 4,810,248, 4,747,837, 4,702,738 and 4,631,057 show hypodermic syringes generally of the type having a slidable tubular sleeve that is in some cases initially retained in a retracted position by yieldable means, for example detent or latching. In the sleeve's retracted position the needle is exposed ready for use. After use, the sleeve is moved to an extended position in which it is latched, and in which the needle is surrounded by the sleeve to prevent accidental injury.
Whereas the primary objective of most of the prior art listed is common with the primary objective of the present invention, that is to protect patients and health care personnel against the potential mortal consequences of accidental skin puncture from a used hypodermic syringe, it is the present invention alone that in combination: First, recognizes a likelihood of an unwanted, premature extension of the protective sleeve during key procedural moments; secondly, provides structure by which a user may interact, by degree, to add to the restraint offered in opposition to a premature extension; thirdly, recognizes the importance of a simultaneous extension of the protective sleeve as the used needle is retracted from the patient; and lastly, provides structure to facilitate a smooth user release of the aforementioned restraint when, after an injection, it comes time to initiate a sleeve extension, simultaneous with needle withdrawal, without need for creating patient pain or discomfort, which might otherwise be the case, should any special user unlatching activity be required as pre-requisite to initiating the sleeve's extension. Primary examples of the referred to, key procedural moments, moments when a premature extension of the sleeve would be likely, are as follows: When removing and attaching needles; when withdrawing the plunger to entrap air; when inserting the needle tip into the medicine supply bottle; when withdrawing the plunger to load medicine into the syringe barrel; and when inserting the needle tip into a patient's body tissue.
U.S. Pat. No. 4,655,751, Harbaugh, appears indirectly to have recognized that there are key procedural times at which a premature extension would be likely, as Harbaugh has provided safeguards against such an extension. Harbaugh, provides ears on the sleeve which lock into pockets recessed into the syringe barrel and would prevent, by "locking", against an unwanted extension at the key procedural moments, as above outlined. In order to release the ears from the pockets at the appropriate time, to facilitate an intentional sleeve extension, the user flexes the somewhat resilient sleeve, distorting its generally cylindrical section into one or more oval in section. This unlatching activity is said to release the ears from the pockets.
The method of Harbaugh's release would seem improper, in terms of it being accomplished while the needle remained in patient tissue because: First there is the probability that a locking type mechanical release could malfunction, or hang up, thereby requiring a good deal of unlatching activity while the needle is deep in patient tissue, thus creating painful discomfort; and secondly because the very squeezing action required to release the ears from the pockets might also deform the resilient sleeve further than intended so that resistance would build at the interface between the sleeve and the barrel, in opposition to the very extension that is being attempted.
Harbaugh fails, as do the other prior art references, to: First, provide a structure which will allow a user interactive role in adding, by degree, to physical restrain in opposition to a premature extension of the protective sleeve; and secondly to develop the concept of a sleeve extension, simultaneous with a needle extraction from a patient, by providing structure which would provide a smooth release of the sleeve from its locked retracted position without special unlatching activity. The present invention alone provides these important features.